Certain fluid dispensing processes require valve assemblies capable of providing both accurate control of the amount of fluid being dispensed and continuous flow of fluid through the valve assembly. One example of such a fluid dispensing process is the dispensing of dye. Continuous flow of dye and other similar fluids through a valve assembly is necessary to prevent fluid stagnation in the valve assembly during time intervals when there is a reduced amount of fluid being dispensed from the valve assembly. Fluid stagnation in the valve assembly can decrease the quality of the fluid being dispensed by allowing the fluid to harden, separate or settle.
Prior art valve assemblies used for dispensing dye maintain a continuous and constant flow through the valve assembly by providing a return or recirculation port. The return port allows fluid to be continuously pumped through the valve assembly so as to eliminate the occurrence of a reduced flow condition which can cause a hardening or settling of the fluid. At least a portion of the fluid entering valve assemblies of the prior art is always recirculated through the return port.
One important disadvantage of the above-discussed valve assemblies of the prior art is that the ability of these valve assemblies to rapidly dispense large volumes of fluid is reduced by the continuous circulation of fluid through the return port. Because a portion of fluid flow passing through the valve assembly is continuously recirculated through the return port, the fluid rate at which the valve assembly is capable of dispensing fluid is limited.
Another problem of prior art valve assemblies capable of recycling fluid is the inability to efficiently replace and repair individual components of the valve assembly.